Method for controlling a variable charge air cooler

ABSTRACT

Embodiments for a charge air cooler are provided. In one example, an engine method comprises during a first mode, decreasing a volume of a charge air cooler in response to a compressor operation upstream of the charge air cooler. In this way, compressor surge may be prevented.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/590,072, entitled “METHOD FOR CONTROLLING A VARIABLE CHARGEAIR COOLER,” filed on Aug. 20, 2012, now U.S. Pat. No. 9,169,809, theentire contents of which are hereby incorporated by reference for allpurposes.

FIELD

The present disclosure relates to an engine including a charge aircooler.

BACKGROUND AND SUMMARY

Turbocharged and supercharged engines may be configured to compressambient air entering the engine in order to increase power. Air flow andpressure fluctuations may result in compressor surge, leading to noisedisturbances, and in more severe cases, performance issues andcompressor degradation. Compressor surge may be controlled by openingone or more compressor recirculation valves in order to route compressedair back to the compressor inlet.

The inventors have recognized an issue with the above approach. Openingthe compressor recirculation valve may reduce the amount of boostprovided to the intake, thus reducing engine output. Further, thecompressor recirculation valve may not provide adequate surge controlunder all conditions. Accordingly, in one embodiment, an engine methodcomprises during a first mode, decreasing a volume of a charge aircooler in response to a compressor operation upstream of the charge aircooler.

In this way, during conditions where compressor surge is likely tooccur, the volume of the charge air cooler may be decreased to maintainthe compressor operation outside of a surge region. In one example, thecharge air cooler may include a valve configured to close during currentor predicted compressor operation in the surge region, allowing theintake air to flow through a subset of the volume of the charge aircooler. The valve may be configured to open during compressor operationin a non-surge region, for example, directing the intake air through theentirety of the charge air cooler. By routing the intake air throughonly a portion of the volume of the charge air cooler instead of theentire volume during surge conditions, intake air flow velocityincreases and compressor surge may be avoided.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example engine including a chargeair cooler.

FIG. 2A shows a schematic diagram of an inlet portion of an examplecharge air cooler intake including a valve in an open position.

FIG. 2B shows a schematic diagram of the charge air cooler intake ofFIG. 2A with the valve in a closed position.

FIG. 3 is a flow chart illustrating a method for controlling air flowthrough a charge air cooler according to an embodiment of the presentdisclosure.

FIG. 4 is a flow chart illustrating a method for performing a clean outcycle of a charge air cooler according to an embodiment of the presentdisclosure.

FIG. 5 is a flow chart illustrating a method for adjusting additionaloperating parameters during the adjustment of the charge air coolervalve according to an embodiment of the present disclosure.

FIG. 6 is a flow chart illustrating a method for controllingturbocharger surge according to an embodiment of the present disclosure.

FIG. 7 is an example map illustrating a surge region according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

The extent of a surge region, which includes compressor operating pointsthat result in surge, may be minimized by decreasing the volume ofintake air downstream of the compressor. According to embodimentsdisclosed herein, a charge air cooler downstream of a compressor mayinclude a valve positioned in the inlet of the charge air cooler thatmay selectively reduce the volume of the charge air cooler. The valvemay be closed in order to reduce charge air cooler volume, and hence thevolume of the intake air downstream of the compressor, responsive tocompressor operation in a surge region.

Furthermore, condensation formation in a charge air cooler may bedetrimental to the engine, as the introduction of the condensate to thecylinders during combustion may cause combustion instability and/ormisfire. Condensation formation may degrade the charge air cooler,particularly if accumulated condensate freezes during an extendedengine-off period. To reduce the accumulation of condensation, the valvepositioned in the inlet of the charge air cooler may be closed toselectively route the intake air through a sub-section of the charge aircooler to increase the velocity of the intake air, relative to thevelocity of the intake air when it travels through an entirety of thecharge air cooler. The valve may be opened or closed in response to acondensation formation value, which provides an estimate of thelikelihood that condensation will form within the charge air cooler.FIG. 1 is a diagram of an engine system including a charge air cooler.The charge air cooler inlet valve is shown in FIG. 2A in its openposition and in FIG. 2B in its closed position. The engine system ofFIG. 1 also includes a controller configured to carry out the methodsdepicted in FIGS. 3-6. The controller of FIG. 1 may also include one ormore maps stored thereon, such as the map depicted in FIG. 7.

First, FIG. 1 is a schematic diagram showing an example engine 10, whichmay be included in a propulsion system of an automobile. The engine 10is shown with four cylinders 30. However, other numbers of cylinders maybe use in accordance with the current disclosure. Engine 10 may becontrolled at least partially by a control system including controller12, and by input from a vehicle operator 132 via an input device 130. Inthis example, input device 130 includes an accelerator pedal and a pedalposition sensor 134 for generating a proportional pedal position signalPP. Each combustion chamber (e.g., cylinder) 30 of engine 10 may includecombustion chamber walls with a piston (not shown) positioned therein.The pistons may be coupled to a crankshaft 40 so that reciprocatingmotion of the piston is translated into rotational motion of thecrankshaft. Crankshaft 40 may be coupled to at least one drive wheel ofa vehicle via an intermediate transmission system (not shown). Further,a starter motor may be coupled to crankshaft 40 via a flywheel to enablea starting operation of engine 10.

Combustion chambers 30 may receive intake air from intake manifold 44via intake passage 42 and may exhaust combustion gases via exhaustmanifold 46 to exhaust passage 48. Intake manifold 44 and exhaustmanifold 46 can selectively communicate with combustion chamber 30 viarespective intake valves and exhaust valves (not shown). In someembodiments, combustion chamber 30 may include two or more intake valvesand/or two or more exhaust valves.

Fuel injectors 50 are shown coupled directly to combustion chamber 30for injecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12. In this manner, fuel injector 50provides what is known as direct injection of fuel into combustionchamber 30; however it will be appreciated that port injection is alsopossible. Fuel may be delivered to fuel injector 50 by a fuel system(not shown) including a fuel tank, a fuel pump, and a fuel rail.

Intake passage 42 may include throttle 21 having a throttle plate 22 toregulate air flow to the intake manifold. In this particular example,the position of throttle plate 22 may be varied by controller 12 toenable electronic throttle control (ETC). In this manner, throttle 21may be operated to vary the intake air provided to combustion chamber 30among other engine cylinders. In some embodiments, additional throttlesmay be present in intake passage 42. For example, as depicted in FIG. 1,an additional throttle 23 having a throttle plate 24 is located upstreamof compressor 60.

Further, in the disclosed embodiments, an exhaust gas recirculation(EGR) system may route a desired portion of exhaust gas from exhaustpassage 48 to intake passage 42 via EGR passage 140. The amount of EGRprovided to intake passage 42 may be varied by controller 12 via EGRvalve 142. Under some conditions, the EGR system may be used to regulatethe temperature of the air and fuel mixture within the combustionchamber. FIG. 1 shows a high pressure EGR system where EGR is routedfrom upstream of a turbine of a turbocharger to downstream of acompressor of a turbocharger. In other embodiments, the engine mayadditionally or alternatively include a low pressure EGR system whereEGR is routed from downstream of a turbine of a turbocharger to upstreamof a compressor of the turbocharger. When operable, the EGR system mayinduce the formation of condensate from the compressed air, particularlywhen the compressed air is cooled by the charge-air-cooler, as describedin more detail below.

Engine 10 may further include a compression device such as aturbocharger or supercharger including at least a compressor 60 arrangedalong intake manifold 44. For a turbocharger, compressor 60 may be atleast partially driven by a turbine 62, via, for example a shaft, orother coupling arrangement. The turbine 62 may be arranged along exhaustpassage 48. Various arrangements may be provided to drive thecompressor. For a supercharger, compressor 60 may be at least partiallydriven by the engine and/or an electric machine, and may not include aturbine. Thus, the amount of compression provided to one or morecylinders of the engine via a turbocharger or supercharger may be variedby controller 12.

Further, exhaust passage 48 may include wastegate 26 for divertingexhaust gas away from turbine 62. Additionally, intake passage 42 mayinclude a compressor recirculation valve (CRV) 27 configured to divertintake air around compressor 60. Wastegate 26 and/or CRV 27 may becontrolled by controller 12 to be opened when a lower boost pressure isdesired, for example.

Intake passage 42 may further include charge air cooler (CAC) 80 (e.g.,an intercooler) to decrease the temperature of the turbocharged orsupercharged intake gases. In some embodiments, charge air cooler 80 maybe an air to air heat exchanger. In other embodiments, charge air cooler80 may be an air to liquid heat exchanger. As described in more detailbelow, charge air cooler 80 may include a valve to selectively modulatethe flow velocity of intake air traveling through the charge air cooler80 in response to condensation formation within the charge air cooler.

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 102, input/output ports 104, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 106 in this particular example, random access memory 108,keep alive memory 110, and a data bus. Controller 12 may receive varioussignals from sensors coupled to engine 10 for performing variousfunctions to operate engine 10, in addition to those signals previouslydiscussed, including measurement of inducted mass air flow (MAF) frommass air flow sensor 120; engine coolant temperature (ECT) fromtemperature sensor 112, shown schematically in one location within theengine 10; a profile ignition pickup signal (PIP) from Hall effectsensor 118 (or other type) coupled to crankshaft 40; the throttleposition (TP) from a throttle position sensor, as discussed; andabsolute manifold pressure signal, MAP, from sensor 122, as discussed.Engine speed signal, RPM, may be generated by controller 12 from signalPIP. Manifold pressure signal MAP from a manifold pressure sensor may beused to provide an indication of vacuum, or pressure, in the intakemanifold 44. Note that various combinations of the above sensors may beused, such as a MAF sensor without a MAP sensor, or vice versa. Duringstoichiometric operation, the MAP sensor can give an indication ofengine torque. Further, this sensor, along with the detected enginespeed, can provide an estimate of charge (including air) inducted intothe cylinder. In one example, sensor 118, which is also used as anengine speed sensor, may produce a predetermined number of equallyspaced pulses every revolution of the crankshaft 40.

Other sensors that may send signals to controller 12 include atemperature sensor 124 at the outlet of the charge air cooler 80, and aboost pressure sensor 126. Other sensors not depicted may also bepresent, such as a sensor for determining the intake air velocity at theinlet of the charge air cooler, and other sensors. In some examples,storage medium read-only memory 106 may be programmed with computerreadable data representing instructions executable by processor 102 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

As described above, FIG. 1 shows only one cylinder of a multi-cylinderengine, and each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector, ignition system, etc.

Turning now to FIGS. 2A and 2B, an inlet side of charge air cooler 80 isdepicted. As depicted in both FIGS. 2A and 2B, charge air cooler 80includes an operable thermal transfer area 202 configured to transferheat from inside the charge air cooler 80 to outside of the charge aircooler 80. The charge air cooler 80 includes a plurality of coolingtubes 204 located in the thermal transfer area 202 of charge air cooler80. The plurality of cooling tubes 204 are in fluidic communication withan inlet tank 206. Inlet tank 206 is configured to receive intake airvia one or more inlet passages 208 coupled to an upstream region of anintake passage (not shown in FIGS. 2A and 2B). The intake air flows fromthe inlet tank 206 to the plurality of cooling tubes 204. After passingthrough the cooling tubes 204, the intake air is routed through anoutlet tank (not shown) coupled to a downstream region of the intakepassage. The charge air cooler 80 may also include a charge air coolervalve 210 configured to change the operable thermal transfer area from afirst volume 214 (shown in FIG. 2A) comprising a relatively large areato second volume 216 (shown in FIG. 2B) comprising a relatively smallarea.

Inlet tank 206 may include a divider 212 that partitions inlet tank 206into a first portion and a second portion. Divider 212 may include oneor more holes. FIG. 2A depicts valve 210 in an open position. When valve210 is open, intake air may pass through one or more holes of divider212 such that intake air flows through both the first and secondportions of inlet tank 206 and through the first volume 214 of thecharge air cooler 80. Substantially all of the plurality of coolingtubes 204 may define the first volume 214. In one example, the chargeair cooler 80 may include 21 cooling tubes, and the first volume 214 mayinclude all 21 cooling tubes.

FIG. 2B depicts valve 210 in the closed position. When closed, valve 210blocks the one or more holes of divider 212. Thus, intake air only flowsthrough the first portion of the inlet tank 206 and through the secondvolume 216 of the charge air cooler 80. A portion of the plurality ofcooling tubes 204 may define the second volume 216. The second volume216 is contained wholly within the first volume 214. That is, thecooling tubes that comprise the second volume 216 also comprise aportion of the first volume 214. Therefore, when valve 210 is closed,intake air flows through only the second volume 216, and when valve 210is open, intake air flows through the first volume 214, which containsthe second volume 216. In one example, the charge air cooler 80 mayinclude 21 cooling tubes, and the second volume 216 may include lessthan 21 cooling tubes. The second volume 216 may include less than halfthe cooling tubes that comprise the first volume 214, such as 9 coolingtubes.

The valve 210 may be, or may be similar to, a flapper valve. The valve210 may include a seat member (e.g., divider 212) comprising asubstantially flat stationary member having one or more holes therethrough. A closure member, for example a flap, or plate may beconfigured to move a first position spaced from the seat member therebyopening the one or more holes wherein intake air is able to flow intothe first volume 214, to a second position adjacent to the seat memberthereby closing the one or more holes wherein intake air is able to flowinto only the second volume 216.

The divider 212 may be part of the valve 210. For example, the divider212 may be a valve seat. The divider 212 may also be a dividing line ordatum, or the like, functionally dividing the charge air cooler 80 intothe two portions. Some embodiments may include two or more dividersdividing the inlet into three or more portions. In some examples one ormore configurations described herein regarding the inlet tank 206 mayinstead, or in addition, be included in an outlet tank (not shown).Substantially all of the plurality of cooling tubes 204 may be in mutualfluidic communication with the outlet tank. It will be understood thatinstead, all the tubes may be in fluid communication on the inlet sideand divided at the outlet side into two or more portions of tubes. Asimilarly configured valve may also be included in the outlet tank andfunction to control whether the fluid is allowed to pass or preventedfrom passing through a similarly configured hole.

Various embodiments may include an actuator (not illustrated) to openand to close the valve 210. The actuator may be one or more of: anelectronic actuator, a vacuum controlled actuator, a mechanical pressurediaphragm, a pulse-width modulated electronic control. When the inletair is allowed to pass through all the tubes of the charge air cooler,i.e. when the valve is open, the inlet air will also experience a dropin pressure and the valve will be exposed on both sides to the pressureof the incoming inlet air. In this way the actuator may only need toprovide a motive force to open and to close the valve in order to changethe valve from an open state to a close state, but may not need toprovide force to keep the flap open or to keep the flap closed.

Thus, FIGS. 2A and 2B depict a charge air cooler configured toselectively direct intake air through either a first, larger volume or asecond, smaller volume via modulation of a valve arranged in the chargeair cooler. In some embodiments, the valve may be mechanically modulatedbased on intake air flow, e.g., the valve flap or plate may be keptclosed by spring tension that is calibrated to match air flow, such thatthe valve flap opens under conditions of high air flow. Thus, during lowair flow conditions, the intake air may be directed through the secondvolume of the charge air cooler, increasing the intake air flow velocitythrough the cooler to prevent condensation accumulation. In otherembodiments, the valve may be controlled by a controller, such ascontroller 12 of FIG. 1, based on various operating conditions. Forexample, the valve may be open during low condensation formationconditions and commanded closed during conditions of high condensationformation. FIG. 3 is a flow chart illustrating a method 300 that may becarried out by a controller according to instructions stored thereon toregulate the position of the valve in the charge air cooler based oncondensation formation.

At 302, method 300 includes determining engine operating conditions. Thedetermined engine operating conditions may include engine speed andload, ambient temperature, MAF, MAP, EGR amount, humidity, and otherparameters. At 304, a condensation formation value is determined fromthe operating conditions. The condensation formation value may be anindicator of the likelihood that condensation will form within thecharge air cooler. In some embodiments, the condensation formation valuemay be the intake air flow velocity determined based on the MAF signal,for example. In another embodiment, the condensation formation value maybe the difference between the dew point of the intake air, determinedbased on the humidity of the intake air and ambient temperature, and thetemperature of the charge air cooler.

Both of the above embodiments for determining a condensation valueestimate the likelihood of condensation formation based one or twosimple factors. However, multiple factors may influence condensationformation within the charge air cooler, such as both the velocity of theair flow and the dew point of the intake air. To provide for anindication of condensation formation with increased accuracy,determining the condensation value may include determining acondensation formation rate based on a model at 306. The model mayinclude inputs of ambient temperature, charge air cooler outlettemperature, mass air flow, EGR flow, and humidity. If the humidity isnot known (for example, if the engine does not include a humiditysensor), the humidity may be set to 100%. As explained above, theambient temperature and humidity may provide an indication of the dewpoint of the intake air, which may be further affected by the amount ofEGR in the intake air (e.g., EGR may have a different humidity andtemperature than the air from the atmosphere). The difference betweenthe dew point and the charge air cooler outlet temperature indicateswhether condensation will form within the cooler, and the mass air flowmay affect how much condensation actually accumulates within the cooler.The condensation formation rate itself may be the condensation formationvalue. In other embodiments, the condensation formation rate may be usedto determine an amount of condensation that has accumulated during agiven time period, and the condensation amount may be the condensationformation value.

A simpler mechanism for determining a condensation value may include acondensation formation value that is mapped to charge air cooler outlettemperature and engine load at 308. Engine load may be a function of airmass, torque, accelerator pedal position, and throttle position, andthus may provide an indication of the air flow velocity through thecharge air cooler. For example, a moderate engine load combined with arelatively cool charge air cooler outlet temperature may indicate a highcondensation formation value, due to the cool surfaces of the charge aircooler and relatively low intake air flow velocity. The map may includea modifier of ambient temperature.

At 310, method 300 includes determining if the condensation formationvalue exceeds a first threshold. The threshold may be dependent on howthe condensation value was determined at 304. For example, if thecondensation formation value is intake air flow velocity, the thresholdmay be a suitable intake air flow velocity above which the surfacetension of the accumulated condensation may break, enabling thecondensation to be entrained with the air flow. If the condensationformation value is the difference between the dew point of the intakeair and the charge air cooler temperature, the threshold may be zero. Ifthe condensation formation rate is determined as the formation value, itmay be compared to a threshold condensation formation rate. If thecondensation formation value is determined based on the temperature/loadmap, the map may provide a numerical value (e.g., between 0-1)indicative of the likelihood of condensation, and this may be compared athreshold.

In some embodiments, the first threshold may be a threshold above whichcondensation forms and below which condensation does not form. In thisway, any indication of condensation may be above the threshold. However,in other embodiments, the first threshold may be set such that a smallamount of condensation is allowed to accumulate.

If the condensation formation value does not exceed the first threshold,method 300 proceeds to 324, which will be explained in more detailbelow. If the formation value does exceed the first threshold, method300 proceeds to 312 to determine if the engine air flow demand is belowa threshold. When the condensation formation value exceeds the firstthreshold, a valve in the charge cooler may be closed to increase intakeair flow velocity and remove and/or prevent condensation accumulation inthe charge air cooler. However, when the valve is closed, the pressuredrop across the charge air cooler increases, limiting air flow to theintake of the engine via the charge air cooler. Thus, the valve in thecharge air cooler may be closed dependent on the air flow demands of theengine such that the valve is kept open if the air flow demands arehigh, to avoid a disturbance in torque. The air flow demand of theengine may be determined based on engine speed and load, manifoldpressure, etc. The threshold air flow demand may be based on the amountof air the charge air cooler is configured to pass when the valve isclosed.

If the engine air flow demand is not below the threshold, method 300proceeds to 324, explained in more detail below. If the air flow demandis below the threshold, method 300 proceeds to 314 to increase theintake air flow velocity through the charge air cooler. As explainedabove, increasing the intake air flow velocity may prevent condensationaccumulation by entraining the condensate within the air flow.Increasing the intake air flow velocity includes closing the valve inthe inlet of the charge air cooler to route the intake air through thesecond, smaller volume of the charge air cooler at 314.

A new condensation formation value may be determined following closingof the valve, and at 318, it is determined if the subsequentcondensation formation value is below a second threshold. In someembodiments, the second threshold may be equal to the first threshold.However, in other embodiments, particularly if the intake air flowvelocity is the condensation formation value, the second threshold maybe lower than the first threshold. If the subsequent condensationformation value is below the second threshold, the valve may be openedat 320; if the condensation formation value is not below the secondthreshold, the valve is kept closed at 322. In this way, thecondensation formation value may be continually monitored and the valvemodulated accordingly. By setting the first and second thresholds to bedifferent, frequent switching around the first threshold may be avoided,particularly when the condensation formation value is intake airvelocity as the opening of the valve will cause a drop in intake airflow velocity.

Returning to 310, if the condensation formation value is not above thefirst threshold, method 300 proceeds to 324 to maintain intake air flowvelocity, which includes, at 326, opening the valve in the inlet of thecharge air cooler (or maintaining the valve in the open position) toroute the intake air through the first, larger volume of the charge aircooler. During extended operation with the valve in the open positionand intake air flowing through the first volume of the charge aircooler, proactive cleaning cycles may be carried out. Thus, at 328,method 300 includes performing a clean out cycle if indicated, whichwill be described in more detail with respect to FIG. 4.

FIG. 4 illustrates a method 400 for performing a clean out cycle of thecharge air cooler. Method 400 may be carried out during the execution ofmethod 300 of FIG. 3, for example it may be periodically carried outwhen the valve in the charge air cooler inlet is in the open position.Method 400 includes, at 402, determining if a charge air cooler cleanout cycle is indicated. As described above with respect to FIG. 3, whenthe condensation formation value is not above the threshold, increasingthe intake air flow velocity may not be necessary to preventcondensation formation, but under certain conditions, the valve may beclosed proactively to clean out the charge air cooler. The conditionsfor initiating a clean out cycle may include extended operation with thevalve in the charge air cooler being in the open position, which maylead to gradual accumulation of condensation within the charge aircooler that periodically necessitates removal.

If a clean out cycle is not indicated, method 400 exits. If a cleancycle is indicated, method 400 proceeds to 404 to determine if theengine air flow demand is below a threshold, similar to the air flowdemand determination described above with respect to FIG. 3. If the airflow demand is not below the threshold, the reduction in volume of thecharge air cooler will reduce the air flow to the intake below the airflow demand, reducing torque. Thus, the clean out cycle is not carriedout, and method 400 exits.

If the air flow demand is below the threshold, method 400 proceeds to406 to determine if the engine is operating with high combustionstability conditions. During the clean out cycle, a slug of condensatemay travel to the engine, which can cause misfire or other unstablecombustion events. To mitigate the unstable combustion events, the cleanout cycle may only be carried out when combustion stability is high sothat the condensate, if present in large enough amounts, may betolerated by the engine. The stable combustion conditions may includelow load, steady state conditions with no or low EGR. If high combustionstability conditions are not present, method 400 may include, at 416,adjusting operating parameters to increase combustion stability. Forexample, the amount of EGR may be reduced. However, in some embodiments,rather than commanding adjustments to operating parameters in order toincrease combustion stability, method 400 may instead include waitinguntil the vehicle is operating with high combustion stability beforecarrying out the clean out cycle.

Once the vehicle is operating with high combustion stability, method 400proceeds to 408 to close the valve in the inlet of the charge air coolerto route intake air through the second volume of the charge air cooler.In contrast to when the valve is closed in response to a condensationformation value, during the clean out cycle, the valve may be controlledin such a manner as to avoid a sudden removal of condensate to theengine. This may include, at 410, slowly ramping the valve closed.Rather than quickly moving the valve and causing a fast increase in theintake air velocity through the charge air cooler, the valve may beslowly closed to gradually increase the intake air velocity. In doingso, the condensate may gradually be routed to the engine. Alternativelyor additionally, the valve may be switched between the open and closedposition at 412 to clean out the condensate in short bursts rather thanin one large amount. Other mechanisms of closing the valve to avoid asudden removal of the condensate are also possible.

At 414, upon completion of the clean out cycle (such as after the valvehas been closed for a threshold amount of time), the valve is returnedto the open position, and control of the valve position continues to bebased on the condensation formation value, as described above.

Thus, the methods described above with respect to FIGS. 3 and 4 providefor selectively routing intake air through a first volume or a secondvolume of a charge air cooler based on a difference between an intakeair dew point and a charge air cooler temperature, the second volumebeing a portion of the first volume. Routing the intake air through thefirst volume comprises opening a valve in the inlet of the charge aircooler, and routing the intake air through the second volume comprisesclosing the valve in the inlet of the charge air cooler. The intake airmay be routed through the first volume when the difference between thedew point and the charge air cooler temperature is below a threshold.The intake air may be routed through the second volume when thedifference exceeds the threshold. The second volume is contained withinthe first volume, such that the first volume comprises the second volumeand an additional volume.

The methods also provide for when a condensation formation value isbelow a threshold, cooling intake air via a first volume of a charge aircooler, and when the condensation formation value is above thethreshold, cooling the intake air via a second volume of the charge aircooler, the second volume being a subset of the first volume. Coolingthe intake air through the first volume comprises opening a valve in theinlet of the charge air cooler, and cooling the intake air through thesecond volume comprises closing the valve in the inlet of the charge aircooler. A plurality of cooling tubes may be located within the chargeair cooler, and the first volume may comprise substantially all of thecooling tubes. The second volume may comprise less than half of thecooling tubes. In some embodiments, the condensation formation value maybe estimated based on mass air flow, ambient temperature, charge aircooler outlet temperature, humidity and an EGR amount. In otherembodiments, the condensation formation value may be estimated based onengine load and charge air cooler outlet temperature. The valve in theinlet of the charge air cooler may be opened under low engine load inorder to provide maximum cooling to the intake air. Under higher loads,such as medium load, the valve may be closed to prevent condensationaccumulation. Under maximum load, the valve may be opened to providemaximum cooling to the intake air.

The system and methods described above provide for opening or closing acharge air cooler valve based on condensation conditions within thecharge air cooler. When the valve is closed, air flow through the chargeair cooler is restricted to a smaller volume. This reduced air flowthrough the charge air cooler may result in a torque disturbance, as asmaller-than-expected amount of air is delivered to the intake of theengine. To compensate for the change in air flow through the charge aircooler, additional operating parameters may be adjusted to maintainrequested torque.

FIG. 5 is a flow chart illustrating a method 500 for adjustingadditional operating parameters in response to an adjustment of thecharge air cooler valve. Method 500 may be carried out by controller 12according to instructions stored thereon. Method 500 includes, at 502,determining engine operating parameters. Engine operating parameters mayinclude engine speed and load, engine temperature, a position of thecharge air cooler valve, condensation conditions within the charge aircooler, and other parameters.

At 504, intake manifold throttle position and turbocharger wastegateposition may be adjusted based on desired torque and boost level. Asexplained above with respect to FIG. 1, the throttle (such as throttle21) may be adjusted according to operator request in order to deliverdesired torque, and the wastegate (e.g., wastegate 26) position may beadjusted based on mass air flow through the turbocharger turbine, inorder to maintain a desired level of boost and/or prevent turbochargersurge or over speed events.

At 506, method 500 includes determining if the charge air cooler valve(such as valve 210) is currently being closed. Determining if the chargeair cooler valve is being closed may include determining if the chargeair cooler is about to be closed, for example by determining if theoperating conditions indicate the valve is to be closed, or if a commandhas been sent to close the valve. As explained previously, the chargeair cooler valve may be closed when conditions in the charge air coolerindicate that condensation may accumulate in the charge air cooler.Additionally, the charge air cooler valve may be closed in response toother parameters, such as compressor surge, explained below with respectto FIGS. 6 and 7.

If the charge air cooler valve is being closed, method 500 proceeds to508 to coordinately adjust additional parameters to maintain torque.Adjusting additional parameters may include adjusting the throttleposition at 510. The initial throttle position may be set based ondriver-requested torque, as explained above. In one example, when thecharge air cooler valve is closed, the throttle may be adjusted to be ina less-restricted position (e.g., more open) in order to prevent furtherlimitations on the air flow to the intake. Adjusting the additionalparameters may also include adjusting the wastegate position at 512.Under some conditions, the reduced air flow through the charge aircooler may be compensated by increasing boost pressure. For example, theboost pressure may be increased by closing the wastegate in order todirect all exhaust through the turbine, increasing the compression ofthe intake air. At 514, adjusting the additional parameters may includeretarding spark timing. If the torque disturbance caused by the closingof the charge air cooler valve is not compensated by the adjustments tothe throttle and wastegate, the spark timing may be adjusted to furthercontrol the amount of torque. In some embodiments, the spark timing maybe retarded prior to the closing of the charge air cooler and thenadvanced back to the predetermined timing once the valve has closed.

Returning to 506, if it is determined that the charge air cooler is notclosing or about to close, method 500 proceeds to 516 determine if thecharge air cooler valve is opening (of if the valve is about to beopened). If the valve is opening, method 500 proceeds to 518 tocoordinately adjust operating parameters to maintain toque. When thevalve is opened, a larger-than-expected amount of air may flow to theintake, causing an increase in torque. To maintain toque at thedriver-requested level, additional operating parameters may be adjustedalong with the opening of the charge air cooler valve. The adjustedparameters may include adjusting the throttle at 520, adjusting thewastegate at 522, and advancing spark timing at 524. In one example, thethrottle may be closed and the wastegate may be opened to counteract theincrease in torque caused by the opening of the charge air cooler valve.The closing of the throttle, opening of the wastegate, and advancingspark timing may be performed prior to the charge air cooler valveopening, or may be performed as the valve is opening.

Returning to 516, if it is determined that the charge air cooler valveis not opening or about to open, method 500 proceeds to 526 to continueto adjust throttle and wastegate position based on desired torque andboost level. If the valve is not opening or closing but is instead in asteady position, no torque disturbances from the charge air cooler arepresent, and thus the throttle and wastegate may be adjusted based ontorque and boost level, respectively, rather than adjusted to accountfor the air flow disturbances from the charge air cooler. Method 500then returns.

While the examples listed above include opening the throttle and closingthe wastegate in response to the charge air cooler valve being closed,under some conditions the throttle may be closed and/or the wastegatemay be opened when the charge air cooler valve is closed. For example,during a transient operating event (such as a decrease engine load), thethrottle may be briefly closed in order to deliver the requested airflow during the transient event. Similarly, under some conditions, thethrottle may be opened and/or the wastegate may be closed when thecharge air cooler valve is opened.

Thus, method 500 provides for an engine method comprising increasingintake air flow velocity through the a charge air cooler, andcoordinately adjusting a position of one or more of an intake manifoldthrottle and a turbocharger wastegate in response to the increasedintake air flow velocity to maintain torque. Increasing intake air flowvelocity may include closing a valve arranged in an inlet of the chargeair cooler to direct air flow through a subset of the charge air cooler,and coordinately adjusting the position of one or more of the intakemanifold throttle and the turbocharger wastegate may include one of moreof opening the intake manifold throttle and closing the turbochargerwastegate as the valve closes. The intake air flow velocity may beincreased in response to an estimated condensation formation valuewithin the charge air cooler, and the condensation formation value maybe estimated based on mass air flow, ambient temperature, charge aircooler outlet temperature, and an EGR amount.

Further, when the estimated condensation formation value is below athreshold, the valve may be open to direct air flow through an entiretyof the charge air cooler, and the intake manifold throttle may be closedand the turbocharger wastegate may be opened as the valve opens. Sparktiming may be adjusted prior to or as the valve closes.

In another embodiment, an engine method comprises selectively routingintake air through a first volume or a second volume of a charge aircooler based on a difference between an intake air dew point and acharge air cooler temperature, the second volume being a portion of thefirst volume, and as the intake air is routed between the first andsecond volumes of the charge air cooler, adjusting one or more of anintake manifold throttle and a turbocharger wastegate position tomaintain torque.

The intake air may be routed through the first volume of the charge aircooler when the difference is greater than a threshold, and routedthrough the second volume of the charge air cooler when the differenceis less than a threshold. To route air through the first volume of thecharge air cooler, a valve arranged in an inlet of the charge air coolermay be opened, and the valve arranged in the inlet of the charge aircooler may be closed to route air through the second volume of thecharge air cooler. The intake manifold throttle may be opened and theturbocharger wastegate may be closed when closing the valve and thethrottle may be closed and the wastegate opened when opening the valve.

In a further embodiment, an engine method comprises when a condensationformation value is below a threshold, cooling intake air via a firstvolume of a charge air cooler by opening a valve arranged in an inlet ofthe charge air cooler, and when the condensation formation value isabove the threshold, cooling the intake air via a second volume of thecharge air cooler by closing the valve, the second volume being a subsetof the first volume. As the valve is opened or closed, one or more of anintake manifold throttle and turbocharger wastegate may be coordinatelyadjusted to maintain torque. Similar to the above embodiments, thethrottle may be opened and the wastegate may be closed when the valve isclosed and the throttle may be closed and the wastegate may be openedwhen the valve is opened.

As explained above, the charge air cooler valve may be adjusted inresponse to compressor operation in a surge region. Compressor surge mayresult from low air flow through the compressor; under certainconditions, such as a driver tip-out event, the flow rate and pressureratio across the compressor can fluctuate to levels that may result innoise disturbances, and in more severe cases, performance issues andcompressor degradation. To mitigate such surge events, volume downstreamof the compressor may be decreased by closing the charge air coolervalve when the compressor is operating near a surge level.

FIG. 6 is a flow chart illustrating a method 600 for adjusting a chargecompressor valve (such as valve 210) in response to compressor operationin a surge region. As used herein and explained in more detail below,the term “surge region” includes compressor operating points that resultin surge (beyond a surge level, for example) as well as operating pointsnear a surge level that do not result in surge (but that may push thecompressor to surge when small air flow fluctuations occur).Additionally, the compressor may be considered to be operating in thesurge region if it is predicted that the compressor would enter surge ator while transitioning to the next requested operating point. Method 600may be carried out by controller 12.

At 602, method 600 includes determining engine operating parameters,such as engine speed and load, boost pressure, mass air flow through thecompressor, compressor pressure ratio, etc. At 604, it is determined ifthe outlet temperature of the charge air cooler is below a threshold. Ifthe temperature is not below the threshold, method 600 proceeds to 606to open the charge air cooler valve. When the temperature at the outletof the charge air cooler exceeds a high temperature threshold, the valvemay be opened to provide maximum air flow, and thus maximum cooling,through the charge air cooler.

If the charge air cooler outlet temperature is below the threshold,method 600 proceeds to 608 to determine if the compressor is currentlyoperating or is predicted to operate in a surge region. The surge regionof the compressor is a function of compressor pressure ratio (e.g.,boost pressure) and air flow through the compressor. The pressure ratioand air flow through the compressor may be mapped to a compressoroperating map, which indicates if the compressor is operating at surge.Alternatively, compressor operation in the surge region may bedetermined based on engine speed and load. Further, even if thecompressor is not currently operating with surge, subsequent operationwith surge may be predicted based on the next requested operating point.For example, if a tip-out event or other drop in engine speed or loadhas occurred, it may be predicted that the air flow through thecompressor is about to decrease, and thus it may be estimated that thecompressor is going to operate in the surge region.

An example compressor operating map 700 is depicted in FIG. 7. Flow ratethrough the compressor is depicted on the x-axis while the pressureratio of the compressor is depicted on the y-axis. An example surge lineis indicated by line 702. The pressure-flow coordinates to the left ofthe surge line 702 are in the surge region 704, where conditions are oflow enough flow and high enough pressure to cause compressor surge.Additionally, the pressure-flow coordinates immediately to the right ofthe surge line 702 may also be in the surge region 704, as they may beso close to the surge line that minor fluctuations in compressor flowmay push the compressor into surge, and thus proactive measures may betaken to avoid surge when the pressure-flow coordinates are within thisarea. All compressor operating points not within the surge region 704may be a non-surge region. The surge line and surge region of map 700are presented as examples, as the surge regions of various turbochargersmay differ depending on turbocharger parameters, such as size.

In one example, at a pressure ratio of 2.5 and flow rate of 5 lbm/min,indicated by dot 706, surge may occur. To avoid surge, the flow ratethrough the compressor may be increased to the reach the surge line, forexample it may be increased by approximately 4 lbm/min to 9 lbm/min, toavoid surge. Alternatively or additionally, to prevent surge, one ormore compressor recirculation valves (CRVs) may be opened and/or thecharge air cooler valve may be closed, as explained below.

Returning to method 600 of FIG. 6, if it is determined at 608 that thecompressor is operating in a surge region or if it is predicted that thecompressor will operate in the surge region, method 600 proceeds to 610to open the CRV in order to increase flow through the compressor. At612, it is determined if the compressor is still operating or predictedto operate within the surge region. If yes, method 600 proceeds to 614to close the charge air cooler valve. By closing the charge air coolervalve, the volume downstream of the compressor is reduced, which maydecrease the compressor's propensity to surge at a given operatingcondition. If the compressor is no longer operating or predicted tooperate within the surge region, method 600 proceeds to 616, which willbe discussed below.

Returning to 608, if it is determined that the compressor is notoperating within the surge region, method 600 proceeds to 616 toestimate a condensation formation value, as discussed above. At 618, thecharge air cooler valve may be adjusted based on the estimatedcondensation formation value. For example, if the condensation value isabove a threshold, the valve may be closed, and if the condensationvalue is below the threshold, the valve may be opened. If the charge aircooler valve is opened, for example, the change in volume downstream ofthe compressor may increase the compressor's propensity to surge. Thus,at 620, the CRV may be opened if the adjustment to the charge air coolervalve pushes the compressor towards surge. The CRV may include aplurality of restriction levels, such that it may be opened in acontinuously variable manner. The position of the CRV may be coordinatedwith the volume change of the charge air cooler to reduce compressorpressure ratio and increase flow to prevent surge. Alternatively, theCRV may be an on/off valve that may only be opened or closed, and amodel may be used to predict when the compressor is going to reach thesurge region, and the CRV may be opened based on the model-predictedsurge operation. In some embodiments, the CRV may be opened only if thecompressor is able to meet the boost demand of the engine with the CRVopen. Additionally, in some embodiments, surge control may be furtherprovided by adjusting the throttle, and maintaining requested torque byadjusting spark timing, camshaft position, etc. Method 600 then returns.

While method 600 adjusts the charge air cooler to control surge afterthe CRV has been opened, other arrangements are possible. For example,the charge air cooler valve may be adjusted anytime the compressoroperates in the surge region, and the CRV valve may be adjusted only ifthe compressor is still operating in the surge region. In anotherexample, both the CRV and the charge air cooler valve may be adjusted ina coordinated manner when operation in the surge region is detected.Furthermore, under some conditions, the charge air cooler valve mayadjusted to provide both surge avoidance and condensation control. Forexample, if condensation conditions indicate that the charge air coolervalve is to be closed and if the compressor is operating with surge, thecharge air cooler valve may be preferentially adjusted instead of or inaddition to the CRV. Conversely, if the compressor is operating in surgeyet the condensation conditions indicate that the charge air coolervalve is to be opened, the CRV may be initially used to control surge,and if the compressor is still operating with surge, then the charge aircooler valve may be closed. The controller may be configured toprioritize condensation management, surge control, and engine air flowand cooling demands in order to determine whether the charge air coolervalve is to be opened or closed.

Thus, method 600 provides for an engine method comprising under a firstcondition, adjusting a volume of a charge air cooler based on acompressor surge condition, and under a second condition, adjusting thevolume of the charge air cooler based on an estimated condensationformation value within the charge air cooler. In some embodiments, thefirst and second conditions may be mutually exclusive, such that thecharge air cooler volume is adjusted based only on the compressor surgecondition or only on the condensation formation value. Such conditionsmay include current or predicted compressor operation in a surge regionas the first condition, and compressor operation in a non-surge regionas the second condition. However, in other embodiments, the first andsecond conditions may not be mutually exclusive.

The volume of the charge air cooler may be adjusted by adjusting acharge air cooler valve arranged in an inlet of the charge air cooler.For example, when the estimated condensation formation value is below athreshold, the charge air cooler valve may be opened to direct air flowthrough an entirety of the charge air cooler, and when the estimatedcondensation formation value is above the threshold, the charge aircooler valve may be closed to direct air flow through a subset of thecharge air cooler. In another example, when the current or predictedcompressor operation is within a surge region, the volume of the chargeair cooler may be decreased by closing the charge air cooler valve.

A compressor recirculation valve may be adjusted when the charge aircooler valve is adjusted. If the position of the charge air cooler valveis adjusted based on the estimated condensation formation value, theposition of the compressor recirculation valve may be adjusted to avoidcompressor surge. Under some conditions, the adjustment to the chargeair cooler valve to avoid surge and/or to control condensation may beoverridden. For example, the charge air cooler valve may be opened ifthe charge air cooler outlet temperature is above a threshold, in orderto provide maximum cooling to the charge air.

It will be appreciated that the configurations and methods disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method of operating an engine having anelectronic control unit including non-transitory instructions stored inmemory, the method comprising: determining engine operating conditions;and coordinately adjusting both a position of a compressor recirculationvalve configured to divert intake air around a compressor and a volumeof charge air flowing through a charge air cooler disposed downstream ofthe compressor, the adjusting based on determined operating conditionsof both the compressor indicating whether the compressor is operating ina compressor surge region and an estimated condensation value of thecharge air cooler.
 2. The method of claim 1, wherein the coordinatelyadjusting the position of the compressor recirculation valve and thevolume of charge air flowing through the charge air cooler includesadjusting the volume of charge air flowing through the charge air coolerby adjusting an actuator of the charge air cooler to adjust a number ofpassages through which the charge air flows within the charge aircooler.
 3. The method of claim 2, wherein the actuator includes a chargeair cooler valve positioned in an inlet tank of the charge air cooler,where the inlet tank includes inlets to the passages through whichcharge air flows within the charge air cooler.
 4. The method of claim 3,wherein the coordinately adjusting includes closing the charge aircooler valve to reduce the volume of charge air flowing through thecharge air cooler, in addition to or instead of adjusting the compressorrecirculation valve, in response to the estimated condensation valuebeing above a threshold and the determined operating conditions of thecompressor indicating that the compressor is operating in the compressorsurge region.
 5. The method of claim 4, wherein the coordinatelyadjusting includes, in response to the determined operating conditionsof the compressor indicating that the compressor is operating in thecompressor surge region and the estimated condensation value being lessthan the threshold, initially adjusting the compressor recirculationvalve and then closing the charge air cooler valve if the compressor isstill operating in the compressor surge region after initially adjustingthe compressor recirculation valve.
 6. The method of claim 3, furthercomprising, in response to extended operation with the charge air coolervalve being in an open position where charge air flows through allpassages through which the charge air flows within the charge aircooler, closing the charge air cooler valve to reduce the volume ofcharge air flowing through the charge air cooler.
 7. The method of claim6, wherein closing the charge air cooler valve includes one of slowlyramping the charge air cooler valve closed and alternating the chargeair cooler valve between open and closed positions.
 8. The method ofclaim 1, further comprising determining the determined operatingconditions of the compressor by at least one of determining a currentcompressor operation in the compressor surge region based on a pressureratio across the compressor and a mass air flow rate through thecompressor and predicting compressor operation in the compressor surgeregion upon transitioning from one operating condition to a nextoperating condition of the engine, based on the current pressure ratioacross the compressor and a mass air flow rate through the compressor atthe next operating condition of the engine.
 9. The method of claim 8,wherein said at least one of the determining the current compressoroperation and the predicting the compressor operation being in thecompressor surge region is based on engine speed and load.
 10. Themethod of claim 8, wherein said at least one of the determining thecurrent compressor operation and the predicting the compressor operationbeing in the compressor surge region is based on the mass air flow ratethrough the compressor and a level of provided boost pressure of thecompressor.
 11. The method of claim 1, wherein the estimatedcondensation value of the charge air cooler is estimated by theelectronic control unit based on one or more of mass air flow, ambienttemperature, charge air cooler outlet temperature, and an exhaust gasrecirculation amount.
 12. A method of operating an engine having anelectronic control unit including non-transitory instructions stored inmemory, the method comprising: determining engine operating conditions;during a first condition when compressor surge of a compressor isexpected and a condensation formation value of a charge air cooler (CAC)is above a threshold, routing intake air through a second volume of theCAC via adjusting a CAC valve based on both the condensation formationvalue above the threshold and determined compressor surge conditions,the second volume being a subset of a first volume of the CAC; andduring a second condition when compressor surge is expected and thecondensation formation value is less than the threshold, opening acompressor recirculation valve and routing intake air through the firstvolume of the CAC via adjusting the CAC valve based on the condensationformation value less than the threshold.
 13. The method of claim 12,further comprising, after adjusting the compressor recirculation valveduring the second condition, adjusting the CAC valve to route intake airthrough the second volume of the CAC in response to determined operatingconditions of the compressor indicating that the compressor is stilloperating in a surge region.
 14. The method of claim 12, wherein the CACvalve is arranged in an inlet tank of the CAC, wherein closing the CACvalve routes intake air from the compressor through the second volume ofthe CAC and blocks air from flowing through a remaining portion of thefirst volume of the CAC, and wherein opening the CAC valve routes intakeair from the compressor through the first volume of the CAC.
 15. Themethod of claim 12, wherein the condensation formation value isestimated based on engine load and CAC outlet temperature.
 16. Themethod of claim 12, wherein the compressor surge conditions includecurrent or predicted compressor operation within a surge region, whereinthe surge region comprises an area of a compressor flow map around asurge line, the surge line based on compressor pressure ratio and massair flow.
 17. The method of claim 12, wherein the compressorrecirculation valve is configured to divert intake air around thecompressor and the CAC is disposed downstream of the compressor in anintake passage of the engine.